1. Field of the Invention
The invention relates to a special angle beam probe for ultrasonic testing with at least one ultrasonic vibrator disposed and fastened in a beam probe housing on a wedge-shaped support body which is formed, in particular, of Plexiglass, and damping means, the ultrasonic beam of the ultrasonic vibrator striking the surface of the test piece at an incidence angle .alpha..noteq.0 relative to the perpendicular or normal of the beam probe, at a point along the surface of the test piece where the beam strikes, the ultrasonic beam further striking the surface of the test piece, and the ultrasonic beam arriving at the surface of the test piece at an oblique angle .delta. subtended between a principal or beam probe reference axis and the U.S. beam, wherein 0.ltoreq..delta..ltoreq.360.degree., as seen in a plan view along the direction perpendicular to the beam probe.
2. Description of the Prior Art:
Such an angle beam probe is known, for instance, from the book "Zerstoerungsfreie Werkstoffpruefung" (non-destructive material testing) by Pal Reti, S. Hirzel Publishers, Stuttgart, Germany, page 196, FIG. 203.
The main areas of application of such angle beam probes are general material testing with ultrasound and in particular the testing of welded seams. Due to the ultrasonic ray incident at an angle with respect to the perpendicular under the incidence angle .alpha., it is possible to detect and evaluate material separations of a given area, which are located perpendicular to or at an angle with respect to the surface, such as cracks and bonding defects. A further area of application of ultrasonic testing with angle beam probes is the testing of disc bodies shrunk-on to shafts in vicinity of shrink fittings and the adjoining regions, especially in vicinity of internal hub surfaces and axial anti-rotation devices in rotor discs of low-pressure turbine rotors. In such cases the rotor discs, as seen in cross section, have lateral faces tapered in the radial direction from the inside out approximately in the shape of a club, up to the rim of the wheel.
As is explained in detail in above-mentioned co-pending U.S. application Ser. No. 613,902 filed May 24, 1984, the geometry of such rotor discs is extremely complicated for ultrasonic testing of the non-accessible inner hub surfaces and axial anti-rotation devices with ultrasonic beam probes. Only the lateral faces of the rotor discs are available as coupling areas for the ultrasonic beam probes. In order to carry out such testing operations, special angle beam probes are required which have a certain incidence angle .alpha. and a certain oblique angle .delta., depending on the wheel disc geometry. The principle of corner reflection of transversal waves is used in this case in the angle-of-impact area of total reflection. This is the so-called corner reflection method, in which the ultrasonic beams are aligned with the test areas of the inner hub surface, and receiving signals are obtained only in the case of flaws. The method of grazing incidence can also be used for checking axial anti-rotation devices.
In order to carry out these testing operations, a multiplicity of special angle beam probes with different pairings of the incidence angle and the oblique angle are required.
It is accordingly an object of the invention to provide special angle beam probe for ultrasonic testing, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, and to generally reduce the number of special angle beam probes required for solving the test problem, so as to thereby simplify stock-keeping and lower the overall testing costs. It is, in particular, an object of the invention to construct a special angle beam probe of this type in such a manner that the manufacture thereof is substantially simplified and less costly as compared to conventional special angle beam probes which are made individually or in a special production run. A purpose of the invention is to produce special angle beam probes with any desired or unusual oblique angles by a relatively small number of basic angle beam probe types with given incidence angles .alpha..
With the foregoing and other objects in view there is provided, in accordance with the invention, a special angle beam probe for ultrasonic testing of a test piece, comprising a multiplicity of prefabricated beam probe subassemblies disposed on a surface of the test piece, the beam probe subassemblies each having a first housing, a wedge-shaped support body disposed in the first housing, at least one ultrasonic vibrator fastened to the support body, and damping means disposed in the first housing, and a multiplicity of second beam probe housings each surrounding a respective one of the beam probe subassemblies, the vibrators each delivering an ultrasonic beam striking a given point along the surface of the test piece at the same predetermined incidence angle other than 0.degree. as measured from a perpendicular or line normal to the surface of the test piece at the given point, the beams arriving at the surface of the test piece at oblique angles between 0.degree. and 360.degree. subtended between a principal or beam probe reference axis of the beam probe and the beam, as seen in direction perpendical to the beam probe from above, the beam probe subassemblies each being fastenable at least at one different predetermined oblique angle in the second beam probe housings, and the second beam probe housings with the beam probe subassemblies having the same incidence angle and different oblique angles being assembled with different oblique angle relationships.
In accordance with an additional feature of the invention, the first beam probe housings have a cylindrical base body having an opening formed in the bottom thereof and having annular shoulder surfaces at the front thereof, the support bodies have coupling surfaces protruding through the openings in the base bodies, and the second beam probe housings have cylindrical guiding surfaces, bottom sliding surfaces and mounting surfaces spaced from the bottom sliding surfaces in axial direction of the beam probe, the cylindrical base bodies of the beam probe subassemblies having the outer periphery thereof inserted and locked in the cylindrical guiding surfaces of the second beam probe housings, setting the predetermined oblique angle by rotation thereof, the annular shoulder surfaces being in engagement with the mounting surfaces defining annular gaps at the bottom of the beam probe for coupling liquid.
In accordance with another feature of the invention, the second beam probe housings are substantially prismatic rectangular bodies each having a central opening formed therein defining the guiding and mounting surfaces, and the second beam probe housings have corner regions having at least two holes formed therethrough and upwardly-protruding pipe stubs or nozzles integral therewith for connecting coupling liquid feedlines.
In accordance with a further feature of the invention, the second beam probe housings are square, as seen from above.
In accordance with an additional feature of the invention, the pipe stubs are diagonally opposite each other.
In accordance with still another feature of the invention, the annular shoulder surface of the cylindrical base bodies are formed on an annular shoulder, the coupling surfaces of the support bodies are formed on bases thereof, the mounting surfaces of the second beam probe housings are formed on a circular inner shoulder or ring collar and are disposed at a given axial distance from the bottom sliding surfaces and the surface of the test piece, and the sum of the height of the annular shoulder and the thickness of the support body base protruding from the base body for each beam probe subassembly is substantially equal to the given axial distance, whereby the bottom sliding surfaces and coupling surfaces are flush.
In accordance with still a further feature of the invention, there is provided a lid liquid-tightly enclosing and shielding the top of the base body.
In accordance with still an additional feature of the invention, there is provided at least one hold-down spring and a clamping screw anchored in a blind tapped hole formed in vicinity of a corner of the second beam probe housing which is free of the holes, the clamping screw tensioning the hold-down spring against the top or the lid of the beam probe subassemblies in each of the second beam probe housings, pushing the beam probe subassemblies against the mounting surfaces.
In accordance with again another feature of the invention, the clamping screw of each of the second beam probe housings has a shank, and the spring is a forwardly curved leaf spring having a hole formed therein through which the shank passes and a free end, the free end having a spherical part centrally disposed on the top or the lid of the beam probe subassembly.
In accordance with again a further feature of the invention, the second beam probe housings only surround part of the height of the beam probe subassemblies, defining protruding free shell regions of the base body, and including at least one connector jack connected to the vibrators and fastened to the free shell regions.
In accordance with again an additional feature of the invention, the at least one connector jack is in the form of at least two parallel-connected connector jacks fastened to two different points of the periphery of each of the base bodies, whereby one of the jacks is always accessible if the other is covered up due to the squint angle.
In accordance with yet another feature of the invention, the axes of the jacks are radially oriented and form a sector angle of substantially 120.degree..
In accordance with yet an additional feature of the invention, the coupling surfaces of the support bodies are formed on bases thereof, and including a first marking on the periphery of each of the bases defining a beam probe reference axis where the oblique angle=0.degree., and the base bodies having a lower peripheral region having a second corresponding counter marking coinciding with the first marking in assembled condition of the beam probe subassemblies.
In accordance with yet a further feature of the invention, the bases of the support bodies are circular discs and the markings are notches.
In accordance with again another feature of the invention, at the point along the periphery of the base bodies having the second markings, the base bodies have radially-oriented posts and the second beam probe housings have radially-extended cuts formed therein receiving the parts, the cuts extending from a point on the guiding surfaces corresponding to the desired squint angle and the cut being exactly matched to the dimensions of the posts for fixing the squint angle without play.
In accordance with again a further feature of the invention, there are provided bearing posts for a gimbal support of a beam probe mounting disposed along another principal axis of the beam probe housing crossing the first-mentioned principal beam probe axis at a right angle on two opposite side walls of the second beam probe housing.
In accordance with still an additional feature of the invention there is provided a spacer bushing mounted on the shank above the top or the lid of the base body.
In accordance with still another feature of the invention, the base body has a gear pitch formed on the outer periphery thereof and the second beam probe housing has a counter gear pitch at the guiding surfaces matching the gear pitch, for changing and securing the oblique angle in accordance with the tooth pitch by rotating the beam probe subassembly relative to the second beam probe housing in angular steps, such as 5.degree..
In accordance with still a further feature of the invention, the second beam probe housing has substantially radial connecting canals formed therein connecting the holes to the annular gap.
In accordance with again an additional feature of the invention, the support body is formed of a material from the group consisting of resinous and plastic material.
In accordance with a concomitant feature of the invention, there is provided a special angle beam probe for ultrasonic testing of a test piece including a prefabricated beam probe subassembly disposed on a surface of the test piece, the beam probe subassembly having a first housing, a wedge-shaped support body disposed in the first housing, at least one ultrasonic vibrator fastened to the support body, and damping means disposed in the first housing, and a second beam probe housing surrounding the beam probe subassembly, the vibrator delivering an ultrasonic beam striking a given point along the surface of the test piece at a predetermined incidence angle other than 0.degree. as measured from a perpendicular to the surface of the test piece at the given point, the beam arriving at the surface of the test piece at an oblique angle between 0.degree. and 360.degree. subtended between a principal axis of the beam probe and said beam, as seen in direction perpendical to the beam probe from above, the beam probe subassembly being fastenable at least at one predetermined oblique angle in the second beam probe housing.